Caveats

let str = "Hello <%= include('file', {person: 'John'}); %>",
      fn = ejs.compile(str, {client: true});
fn(data, null, function(path, d){ // include callback
  // path -> 'file'
  // d -> {person: 'John'}
  // Put your code here
  // Return the contents of file as a string
}); // returns rendered string